1. Field of the Invention
The present invention relates to the improvement of an apparatus for joining an end of a thin metal pipe to a flange joint, this type of pipe having a relatively small diameter, i.e., 50 m/m in pipe diameter and approximately 2 m/m or less in wall thickness and being widely utilized for arrangement of passageways for supplying the air and oil to an automobile, a variety of machines, equipments and devices.
2. Description of the Prior Art
This kind of conventional joining apparatus is constructed in such a way that: an end of a metal pipe (P') is at first inserted into an assembly hole (12) perforated in the axial core portion of a flange member (11) so as to be welded to each other by heat-brazing (W); a communication hole (15) formed in a corresponding installation base (13) is next made coaxial with the metal pipe (P') in order to fasten the flange joint to the base (13) with a bolt; and a sealing (14) is interposed between the outer periphery of the metal pipe (P') and the inner periphery of the comminication hole (15).
However, the following problems inherent in the conventional structure arise. There is created deterioration in mechanical strength which lies in fragility caused by the local heating in the vicinity of the brazing-welded portion of the pipe (P') because of a remarkable difference in wall thickness between the pipe (P') and the flange member (11), the local heating being derived from unaccustomed and inexperienced operations when performing the welding process based on heat-brazing with a burner or the like. This induces a crack and breakdown in the vicinity of the brazing-welded portion (W) of the pipe (P') due to such factors as uneveness in product bending configuration of the pipe (P') and the arrangement under an exciting condition caused by forcible installation relative to the discordance. Since the joining process is based on the brazing-weld, in some cases the soder is dropped and stuck to the installation surface of the flange member (11), and it is unfeasible to employ the flange member 11) and the pipe (P') which have previously been subjected to anticorrosive coating process by plating. Hence, there is no alternative but to effect the coating process after the brazing-weld (W) has been finished. This requires troublesome treatment, which will further bring about a decrease in effeciency of processing.